They are obviously having a BBQ and have been just chatting (fairly loudly) most of the night. All fine.
Now that it is later, try are getting noisier and noisier. It isn't just loud chatting and laughing but full blow whoa ho ho or wahey at the top of their voices.
AIBU to think that yelling and screaming at this time of night is rude. These are adults by the way and not kids.
I have had to shut my windows which means I'm not getting much sleep tonight.
Surely now it's later they can move inside. Behind our back gardens are sheltered accommodation.